1. Field of the Invention
The invention relates to the field of computer communications, and more particularly, to providing a fail-safe communications network applicable to, for example, a power control network.
2. Background Information
In previous communications networks, such as the SPCN (System Power Control Network) which is disclosed in U.S. Pat. No. 5,117,430, nodes in the network were connected as two open ended chains of secondary nodes extending from a primary node. The SPCN was designed as a low volume serial network used to monitor power conditions at a plurality of nodes in a computer system, in particular, the IBM AS/400 (IBM and AS/400 are registered trademarks of International Business Machines Corporation). The nodes typically include microprocessors which monitor the status of, and make occasional adjustments to, the power conditions at the respective nodes. However, this prior network arrangement had several limitations.
As can be appreciated, a failure of a secondary node or the cable interconnection between nodes in the network could make all secondary nodes downstream of the failure inaccessible to the system. The network manager would only be able to pinpoint the point of the failure to two adjacent nodes and their interconnection.
Further, there was also a directionality to the connections of the secondary nodes. In particular, the secondary nodes had dedicated input and output ports for receiving and forwarding commands, respectively. The system would not function properly if it was miswired, for example, if a command input port were mistakenly connected to the network as an output port, since the secondary nodes would only accept commands from an input port.
This directionality also presented a problem if it was desired to connect all the nodes of a network in a loop by simply connecting the ends of each chain together. A loop configuration provides two ways to communicate with each node to provide fault tolerance and the ability to more accurately determine the precise location of the failure.
The inability to connect the nodes in a loop configuration also precluded the connection of two or more separate systems into a single configuration since without the loop configuration, it is not possible for the primary nodes of each system to communicate in the event of failures. This prevents one primary node from taking over network management responsibilities from a failing primary node.
Therefore, a need existed for an enhanced communications network to overcome these and other limitations of the prior network systems.